Microwave cable cooling

ABSTRACT

A cable cooling apparatus, for dissipating heat generated by a cable, includes a housing configured for attachment to at least a portion of cable, the housing being configured to retain a meltable material in a first state and the meltable material configured to dissipate thermal energy from the cable during transformation to a second state.

BACKGROUND

1. Technical Field

The present disclosure relates generally to energy transmission for medical/surgical ablation devices and assemblies and methods of their use. More particularly, the present disclosure relates to cooling microwave energy transmission cables that deliver microwave energy to microwave antenna devices and assemblies.

2. Background of Related Art

Tissue has been found to denature at elevated temperatures (which are slightly lower than temperatures normally injurious to healthy cells). These types of elevated-temperature treatments, known generally as hyperthermia therapy, typically utilize electromagnetic radiation to heat diseased cells to temperatures above 41° C. The body may maintain healthy cells adjacent the diseased tissue at a lower temperatures where irreversible cell destruction will not occur by maintaining sufficient blood flow. Other procedures utilizing electromagnetic radiation to heat tissue also include ablation and coagulation of the tissue. Such microwave ablation procedures, e.g., such as those performed for menorrhagia, are typically done to ablate and coagulate the targeted tissue to denature or kill it. Many procedures and types of devices utilizing electromagnetic radiation therapy are known in the art. Such microwave therapy is typically used in the treatment of tissue and organs such as the kidney, lung, prostate, heart, and liver.

One minimally invasive procedure generally involves the treatment of tissue (e.g., a tumor) underlying the skin via the use of microwave energy. Tissue may be accessed percutaneously, or through the skin, and the microwave energy further penetrates the adjacent tissue to ablate large areas of tissue. However, treatment with microwave energy requires the transmission of energy at microwave frequencies from an electrosurgical generator to an ablation device and the transmission often results in problems such as inadvertent discharge of microwave energy and/or transmission line heating.

Although there are various means for transmitting microwave energy, the most common means in medical ablation involves use of a coaxial cable. While high quality coaxial cables are designed and manufactured to minimize and/or eliminate inadvertent discharge of microwave energy all coaxial cable experiences a temperature increase while delivering microwave energy.

The present disclosure describes a coaxial cable cooling apparatus including a housing with various active and passive cooling means and methods.

SUMMARY

The present disclosure relates generally to energy transmission for medical/surgical ablation devices and assemblies and methods of their use. More particularly, the present disclosure relates to cooling microwave energy transmission cables that deliver the microwave energy to microwave antenna devices and assemblies.

A cable cooling apparatus, for dissipating heat generated by a cable, includes a housing and a meltable material. The housing is configured for attachment to at least a portion of a cable and configured to retain the meltable material. The meltable material, disposed within the housing, is configured to dissipate thermal energy from the cable during transformation to a second state. The temperature at which the material transforms from a first state to a second state may be between about 40° C. and about 100° C. The meltable material may be selected from a group consisting of animal wax, insect wax, vegetable wax, mineral wax, petroleum wax, synthetic wax and an evaporative material. The coaxial cable may be a microwave energy transmission cable.

In a further embodiment of the present disclosure the housing may further include at least one inlet and one outlet formed in the housing. The at least one inlet may be in fluid communication with the meltable material and configured to receive a fluid. The at least one outlet may be in fluid communication with at least one of the inlets and configured to discharge the fluid from the housing. The fluid may be a thermally conductive fluid and may be selected from a group consisting of water, saline, ammonium chloride, sodium nitrate, and potassium chloride. The cable may be a microwave energy transmission cable.

In another embodiment of the present disclosure, cable cooling apparatus, for dissipating heat generated by a cable, includes a housing defining a fluid-tight cavity therewithin, the housing disposed on at least a portion of a cable and configured to cool at least a portion of the cable. The housing includes at least one inlet configured to receive a fluid for cooling and at least one outlet, in fluid communication with the at least one inlet, for discharging the fluid from the housing. The fluid enters the housing through the inlet, is circulated through at least a portion of the housing and absorbs thermal energy from at least a portion of the cable. The housing may surround at least a portion of the cable.

In a further embodiment of the present invention the housing may further include a cooling portion in thermal communication with the cable and a return portion for returning fluid through the at least one outlet. The cooling portion and the return portion may be formed of one of a multi-lumen tube, two or more paratubes, and a concentrically orientated multi-lumen tube. The coaxial cable may be a microwave transmission cable and the housing may be in direct contact with the outer conductor of the coaxial cable.

In yet another embodiment of the present disclosure a method for cooling a microwave energy transmission cable during energy transmission through the cable is provided. The method includes the steps of positioning at least one cable cooling apparatus adjacent a microwave energy transmission cable; transmitting energy through the energy transmission cable; and dissipating heat produced by the energy transmission cable, during the energy transmission, through the at least one cable cooling apparatus.

The cable cooling apparatus may include a plurality of cable cooling apparatus along the microwave energy transmission cable. The cable cooling apparatus may contain a selectively meltable material configured to dissipate heat from the microwave energy transmission cable. When heated, the meltable material may change from a first state to a second state.

In a further embodiment of the present disclosure the method may include the steps of providing a cooling fluid to the at least one cable cooling apparatus and circulating the fluid therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a system for performing medical/surgical ablation with a plurality of cooling apparatus, according to an embodiment of the present disclosure, disposed on a coaxial cable thereof;

FIG. 2A is a perspective view of a hinged cooling apparatus according to an embodiment of the present disclosure;

FIG. 2B is a transverse cross-sectional view of the hinged cooling apparatus of FIG. 2A;

FIG. 3A is a perspective view of a slip-on cooling apparatus according to an embodiment of the present disclosure;

FIG. 3B is a transverse cross-sectional view of the slip-on cooling apparatus of FIG. 3A;

FIG. 4A is plan view of cooling apparatus with an elongate body, according to another embodiment of the present disclosure, disposed on a coaxial cable of the surgical ablation system;

FIG. 4B is a plan view of the cooling apparatus of FIG. 4A;

FIG. 4C is a plan view of the cooling apparatus of FIG. 4B with an elongate body configured to form a single wrap on a coaxial cable;

FIG. 5 is an illustration of a system for performing medical/surgical ablation including a plurality of cooling apparatus with fluid cooling, according to an embodiment of the present disclosure, disposed on a coaxial cable of the surgical ablation system;

FIG. 6 is a perspective view of the hinged cooling apparatus of FIG. 2A with fluid cooling;

FIG. 7 is a perspective view of the slip-on cooling apparatus of FIG. 3A with fluid cooling;

FIG. 8A is plan view of a multi-lumen cooling apparatus, according to an embodiment of the present disclosure, disposed on a coaxial cable of the surgical ablation system;

FIG. 8B is a plan view of the multi-lumen cooling apparatus of FIG. 8A;

FIG. 8C is a transverse cross-sectional view of the multi-lumen cooling apparatus of FIG. 8B as taken through 8C-8C of FIG. 8B;

FIG. 9 is a perspective view of a system for performing medical/surgical ablation with a cooling sleeve apparatus, according to yet another embodiment of the present disclosure, disposed on the coaxial cable of the surgical ablation system;

FIG. 10A is a transverse cross-sectional view of one embodiment of the cooling sleeve apparatus of FIG. 9 with a cooling body filled with fluid and pressed against the coaxial cable;

FIG. 10B is a transverse cross-sectional view of the cooling sleeve apparatus of FIG. 9 with the cooling body empty;

FIG. 10C is a transverse cross-sectional view of another embodiment of the cooling sleeve apparatus in FIG. 9 with the cooling body filled with fluid and pressed against the coaxial cable; and

FIG. 10D is a transverse cross-sectional view of the cooling sleeve apparatus of FIG. 9 with the cooling body empty.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the presently disclosed coaxial cable cooling apparatus will now be described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. As used herein and as is traditional, the term “distal” refers to the portion that is furthest from the user and the term “proximal” refers to the portion that is closest to the user. In addition, terms such as “above”, “below”, “forward”, “rearward”, etc. refer to the orientation of the figures or the direction of components and are simply used for convenience of description.

Medical ablation of tissue is increasingly performed using microwave energy. Microwave energy is typically delivered to an electrosurgical energy delivery apparatus, such as a microwave antenna assembly, through a coaxial cable. Referring now to FIG. 1, a system for delivering microwave energy, including at least one coaxial cable cooling apparatus 100 according to an embodiment of the present disclosure, is shown as 10. The microwave delivery system 10 includes a microwave generator 15, a coaxial cable 20 operatively connected or coupled to generator 15, at least one coaxial cable cooling apparatus 100 disposed on coaxial cable 20, and an electrosurgical energy delivery apparatus 30 including at least one microwave antenna 30 a capable of transmitting microwave energy.

As seen in FIG. 1, coaxial cable cooling apparatus 100 (hereinafter “cooling apparatus 100”) includes a cooling body or housing 105 configured to attach to at least a portion of the coaxial cable 20. At least a portion of the housing 105 is configured to absorb thermal energy from at least a portion of the coaxial cable 20. Housing 105 may include a cooling portion and a thermal dissipation or thermal energy removal portion. Cooling portion may include a passive cooling means, such as, for example, thermal energy absorbing material with a high thermal mass, energy storage through material phase change, or a thermal energy exchanging means, an active cooling means, such as, for example, fluid cooling, or any suitable combination thereof. Thermal dissipation or thermal energy removal portion may provide a means of removing thermal energy from the coaxial cable 20 and/or cooling apparatus 100. Various passive and active cooling means in accordance with the present disclosure are disclosed hereinbelow.

As seen in FIG. 1, microwave delivery system 10 may include a plurality of cooling apparatuses 100 spaced from each other and disposed on the coaxial cable 20. Positioning and spacing between the cooling apparatuses 100 on the coaxial cable 22 may be dependant on a number of factors. Factors include the thermal energy generated by the coaxial cable 20, the thermal mass of the individual cooling apparatus 100, the thermal energy absorption rate of the individual cooling apparatus 100 and one or more characteristics of the microwave energy, such as, for example, the frequency, phase and power of the microwave energy. The thermal energy generated by the coaxial cable 20 may depend upon the medical procedure including the length of time of the procedure, the energy delivered during the procedure, the energy loss characteristics of the cable, the frequency of the energy, the type of tissue targeted by the procedure, and the type of device used for the procedure. The number of cooling apparatus 100 may depend on the spacing determined by the factors discussed above and the total length of the coaxial cable 20. In one embodiment, only a single cooling apparatus 100 is utilized.

The position of the hot spots on the coaxial cable 20 may vary and may even move during a procedure thus making placement of the cooling apparatus 100 on an individual hot spot difficult. As an alternative to placing cooling apparatus 100 directly on hot spots, a plurality of cooling apparatus 100 may be placed on coaxial cable 20 to provide uniform cooling of the coaxial cable 20. For example, spacing between hot spots on a coaxial cable may be related to a characteristic of the wavelength, e.g., hot spots may be spaced every half wavelength along the length of the coaxial cable. To provide uniform cooling of the cable, cooling apparatus 100 may be spaced uniformly along the coaxial cable 100 with the center of each cooling apparatus spaced one-half wavelength apart. While each individual cooling apparatus 100 may not be positioned directly on a hot spot, the distance from a cooling apparatus 100 to a hot spot, along the coaxial cable 20, will be uniform.

Passive Cooling

Cables used for transmitting microwave energy are typically designed for efficient transmission of microwave energy without discharge or loss of microwave energy. Examples of suitable cables include a coaxial cable, a triaxial cable and a double sheathed coaxial cable. Although any suitable cable is contemplated by the present disclosure, in the illustrated embodiment of FIGS. 2A and 2B, a coaxial cable 20 includes an outer sheath 22, an outer conductor 24, an inner conductor 26 and a dielectric 28 between the outer conductor 24 and the inner conductor 26. Efficient transmission of microwave energy, with minimal amount of microwave energy discharge or loss, requires the inner conductor 26 to be positioned at the approximate radial center of the outer conductor 24. The dielectric 24 both positions the inner conductor 26 at the approximate radial center of the outer conductor 24 and insulates the inner conductor 26 and outer conductor 24 by providing a uniform impedance between the inner and outer conductors 26, 24.

The construction of a coaxial cable 20, to efficiently transmit microwave energy, results in a coaxial cable 20 with excellent transmission properties and typically with very little thermal mass. As a result, during electrosurgery using microwave energy, particular amounts of energy discharged within the coaxial cable may elevate the temperature of the coaxial cable to unacceptable levels. Cable heating is more prevalent with small, flexible cables that are needed when manual manipulation of the cable is required such as, for example, during the placement of a delivery apparatus 30.

With continued reference to FIG. 2A, a cooling apparatus 200, in accordance with an embodiment of the present disclosure, is at least partially disposed on coaxial cable 20. Cooling apparatus 200 includes a cooling body or housing 205 configured to absorb thermal energy from at least a portion of the coaxial cable 20. Housing 205 includes an upper housing portion 205 a and a lower housing portion 205 b inter-connected by a hinge-member 207 (e.g., piano hinge, living hinge, etc.), or other suitable connector. Cooling apparatus 200 may be reusable or disposable and may be either temporarily or permanently attached to the coaxial cable 20.

Cooling apparatus 200 may include an attachment means to affix housing 205 to the coaxial cable 20. As illustrated in FIG. 2A, attachment means may include at least one latch 210 extending from the upper housing portion 205 a that enters a corresponding slot 215 formed in the lower housing portion 205 b. Attachment means may lock the cooling apparatus 200 onto the coaxial cable 20. A latch release 217 is provided to slide in the direction of the arrow “A” to release latch 210 from slot 215. Others suitable means of attaching the housing 205 onto the coaxial cable may be used.

In accordance with an embodiment of the present disclosure, the cooling apparatus 200 includes a thermal mass that is greater than that of the coaxial cable 20 disposed therewithin. Attaching a cooling apparatus 200 such that cooling apparatus 200 is in thermal contact with the coaxial cable 20 increases the overall thermal mass of the body, i.e., the combined thermal mass of the coaxial cable 20 and the cooling apparatus 200. In use, upper housing portion 205 a and/or the lower housing portion 205 b may draw thermal energy away from, and thereby cool, the coaxial cable 20. Alternatively, increasing the thermal mass of the body, by attaching one or more cooling apparatus 200, may decrease the rate at which the cable temperature increases.

In use, cooling apparatus 200, while disposed on and absorbing thermal energy from coaxial cable 20, may not alter and/or significantly change the physical properties of the coaxial cable 20, e.g., the spacing and/or positioning of the inner conductor 26, dielectric layer 28 or outer conductor 24 relative to each other. Additionally, cooling apparatus 200 may not alter and/or significantly change the electrical properties of the coaxial cable 20, e.g., cable impedance and/or conductive properties thereof.

As seen in FIG. 2A, an inner surface 205 b of the cooling apparatus 200 is configured to contact the sheath 22 of the coaxial cable 20 when cooling apparatus 200 is operatively connected or coupled thereto. In yet another embodiment of the present disclosure, at least a portion of cooling apparatus 200 may pierce the sheath 22 and make direct thermal contact with outer conductor 24. Direct thermal contact between the cooling apparatus 200 and outer conductor 24 may be desirable to increase the rate of thermal energy removal from the coaxial cable 20. Alternatively, a portion of the sheath 22 may be removed to allow direct thermal contact between cooling apparatus 200 and outer conductor 24.

FIG. 2B is a traverse cross-sectional view of the cooling apparatus 200 of FIG. 2A with the upper housing portion 205 a in an open position (shown in phantom) and in a closed position. In a closed position, the upper housing portion 205 a is adjacent the lower housing portion 205 b. As indicated by arrow “B”, the upper housing portion 205 a may pivot relative to the lower housing portion 205 b between a closed position and an open position.

To place the cooling apparatus 200 on the coaxial cable 20, the coaxial cable 20 is placed in the upper or lower housing portion 205 a, 205 b while cooling apparatus 200 is in an open position. The upper and lower housing portions 205 a, 205 b are then reposition to a closed position and latch 210 in upper housing portion 205 a connects with slot 215 in lower housing portion 205 b, thereby locking cooling apparatus 200 on coaxial cable 20. Cooling apparatus 200 may be removed from coaxial cable 20 by sliding latch release 217 in the direction of arrow “A” (see FIG. 2A), disengaging latch 210 from slot 215 and repositioning the upper and lower housings 205 a, 205 b to an open position.

Housing portions 205 a, 205 b may each define respective cavities 225 for containing material 220 therein, the material 220 having a high thermal mass and/or high energy absorbing properties. In one embodiment, housing 205 may contain a meltable material 220 a, such as wax, disposed within the cavity 225 of housing portions 205 a, 205 b. The meltable material 220 a may be solid at room temperature or before cooling apparatus is disposed on the coaxial cable 20. Meltable material may be any suitable material that exhibits a phase change while absorbing thermal energy. Phase change may be from a solid to a liquid, from a liquid to vapor or any other suitable phase change that results in the meltable material absorbing thermal energy. The melting point or temperature at which the phase change of the meltable material 220 a occurs should be below any unacceptable high temperature for the coaxial cable 20. Various types of waxes may be suitable because, depending on the specific wax used, the melting point may be between about 40° C. and about 100° C. Cavities 225 of housing portions 205 a, 205 b may be fluid tight thereby sealing the meltable material 220 a therewithin.

In another embodiment, material 220 may include a semi-solid or gel. Cooling may occur as the material evaporates from a semi-solid state to vapor or sublimates from solid to a gel.

Meltable material 220 a may be, solid, soft, pliable or formable prior to the application of the cooling apparatus 100 to coaxial cable 20 to allow housing 205 to conform to coaxial cable 20. Alternatively, the meltable material 220 a may be granulated, microcapsulated or powderized thus allowing an otherwise hard meltable material 220 a to generally conform to the coaxial cable 20. In addition, granulating, microcapsulating or powderizing a meltable material 220 a may decrease the individual particle size and increases the overall surface area of the meltable material 220 a and may result in an increase in the rate of thermal energy absorption of material 220 a.

In another embodiment, material 220 may include a meltable material 220 a and at least one thermally conductive material 220 b, such as, for example, aluminum or iron. The thermally conductive material 220 b may be homogenously mixed with the meltable material 220 a such that thermally conductive material 220 b distributes the thermal energy throughout the cavities 225 and the meltable material 220 a absorbs the thermal energy. The homogenous mixture of a meltable material 220 a and a thermally conductive material 220 b may result in material 220 with a high thermal mass and a high rate of thermal energy absorption. Addition of the thermally conductive material 220 b may evenly distribute the thermal energy throughout cavity 225 of housing portions 205 a, 205 b.

Alternatively, thermally conductive material may not be homogenously mixed with the meltable material. Instead, thermally conductive material may be positioned within the cavities such that thermal energy is drawn away from the coaxial cable 20, such as, for example, fins similar to that of a heat exchanger.

The meltable material 220 a may be a wax selected from a group including insect wax, vegetable wax, mineral wax, animal wax, petroleum wax, synthetic wax and any suitable combination thereof.

Usable insect waxes include but are not limited to beeswax, produced by honey bees, with a melting point between about 61° C.-66° C.; Chinese wax, produced by scale insects such as Coccus ceriferus and Brahmaea japomca (Coccoidea), with a melting point between about 82° C.-84° C.; wax produced by the Icerva purchasi and Dactylopius coccus, with a melting point of about 78° C. and between about 99° C.-101° C., respectively; and Shellac, a wax is secreted by the Lac insect, with a melting point between about 74° C.-78° C.

Useful vegetable waxes include but are not limited to Bayberry wax, from the surface of the berries of the bayberry shrub, with a melting point of about 45° C.; Candelilla wax, from the Mexican shrubs Euphorbia cerifera and E. antisyphilitica, with a melting point between about 67° C.-79° C.; Carnauba wax, from the leaves of the Carnauba palm, with a melting point between about 78° C.-85° C.; Castor wax, formed from hydrogenated castor oil, with a melting point between about 61° C.-69° C.; Japan wax, formed from a byproduct of lacquer manufacture, with a melting point of about 53° C.; Ouricury wax, from the Brazilian Feather palm, with a melting point between about 81° C. and 84° C.; and Rice bran wax, obtained from rice bran, with a melting point between about 77° C.-86° C.

Usable mineral waxes include but are not limited to Montan wax, extracted from lignite and brown coal, with a melting point between about 82° C.-95° C.; and Ozocerite, a naturally occurring wax found in lignite beds, with a melting point between about 58° C.-100° C.

Usable animal waxes include but are not limited to Spermacet, obtained from the head cavities and blubber of the sperm whales and Lanolin, also known as wool wax, obtained from the sebaceous glands of sheep with a melting point between about 35° C.-42° C.

Usable petroleum waxes include but are not limited to Paraffin wax, made of long-chain alkane hydrocarbons, with a melting point between about 47° C.-64° C.; and Microcrystalline wax, produced by de-oiling petrolatum, with a melting point between about 60° C.-80° C.

Usable synthetic waxes including but are not limited to polyethylene waxes, based on polyethylene, and waxes chemically modified such as, for example, esterified or saponified, substituted amide waxes and polymerized α-olefins.

Material 220 may include any suitable material, or mixture of materials, capable of absorbing and retaining a thermal load.

Turning now to FIGS. 3A and 3B, another embodiment of a cooling apparatus 300 of the present disclosure is shown. Cooling apparatus 300 includes a cooling body or housing 305 forming a lumen 330 in the approximate radial center of the cooling housing 305. Access to the lumen 330 is provided by a channel 335 extending through housing 305 and extending an entire length thereof. Housing 305 is sufficiently flexible such that housing 205 can be manipulated to open or expand channel 335, in the direction of the opposing arrows “C”, to allow coaxial cable 20 to slip through channel 335 and into lumen 330.

Once coaxial cable 20 is disposed in lumen 330 a flap 340, fastened to housing 305 on one side of channel 335, may be used to close the channel 335 by selectively attaching to housing 305 at a flap attachment area 340 a on the second side of channel 335. Flap attachment area 340 a may use any suitable attachment means, such as, for example, hook and loop type fasteners, adhesive, tape, snaps, buttons or latches. To remove cooling apparatus 300 from coaxial cable 20 flap 340 is detached from the flap attachment area 340 a, channel 335 is opened by pulling the housing 305 in the direction of the opposing arrows “C” and the coaxial cable 20 is removed from lumen 330.

The diameter of lumen 330 is sized to be substantially equal to an outer diameter of the coaxial cable 20 such that when the channel 335 is closed, with the coaxial cable 20 in the lumen 330, the housing 305 makes substantial contact with a length of the coaxial cable 20.

As illustrated in the cross-sectional view in FIG. 3B, housing 305 forms a chamber 325 that contains thermal energy absorbing material 320 as discussed hereinabove. Material may be contained within chamber 325 by a fluid-tight manner.

In yet another embodiment of the present disclosure, an internal surface of the housing 305 within the lumen 330 may pierce the sheath 22 and make thermal contact with the outer conductor 24 to facilitate the removal of thermal energy from the coaxial cable 20.

As seen in FIGS. 4A-4C, another embodiment of a cooling apparatus 400 of the present disclosure is shown. Cooling apparatus 400 includes an elongate cooling body 405 in the form of a tape-like structure for wrapping coaxial cable 20. Cooling apparatus 400 may be wrapped along or around coaxial cable 20, as illustrated in FIG. 4A. Cooling apparatus 400 includes a flap 440 on each end of cooling body 405 that attaches to a flap landing area 440 a and secures cooling apparatus 400 to the coaxial cable 20. Housing 405 contains thermal energy absorbing material as discussed in the embodiments above.

The length of coaxial cable 20 covered by the cooling apparatus 400 is determined by the width of the cooling body 405, the pitch or angle of the wrap, the amount of overlap between two adjacent wraps, the diameter of the coaxial cable 20 and the length of the cooling apparatus 400. For example, FIGS. 4A and 4B illustrate a cooling apparatus 400 wrapped approximately four times around a coaxial cable 20, with little or no overlap between wraps, at a pitch of approximately 45 degrees. The length of coaxial cable 20 covered by the cooling apparatus 400 may be approximately four times the width of the cooling body 405.

FIG. 4B illustrates an extended or unwrapped cooling apparatus 400 of FIG. 4A. The length and width may be larger or smaller based on the dimensions of coaxial cable covered by the cooling apparatus 400. Increasing the length of cooling apparatus 400 may increase the number of times the cooling apparatus 400 will wrap around the coaxial cable 20. Increasing the width of cooling apparatus 400 may increase the amount of coaxial cable 20 covered by each wrap.

Returning to FIG. 4A, the size of each flap 440 and the size and position of each flap attachment area 440 a on the cooling apparatus 400 may be adjusted for different coaxial cable 20 dimensions. For example, the center of the flap 440 and the center of the flap attachment area 440 a are spaced such that when the cooling apparatus 400 is wrapped around the coaxial cable 20 the flap 440 folds onto at least a portion of the flap attachment area 440 a. The spacing between the flap 440 and the flap attachment area 440 a is about equal to, or greater than, the circumference of the coaxial cable 20. Spacing between the flap 440 and the flap attachment area 440 a may be adjusted for larger diameter or smaller diameter coaxial cables.

As seen in FIG. 4C, a cooling apparatus 401 is provided and includes a single-wrap around a portion of the coaxial cable. Cooling apparatus 401 may be applied to specific hot-spots in or along the transmission path, such as, for example, connections to the coaxial cable, connections between two coaxial cables and bends or kinks in a coaxial cable.

The cooling apparatus 100, 200, 300, 400 and 401 with passive cooling discussed hereinabove are attached to a coaxial cable 20 thereby increasing the thermal mass of the body. During energy delivery the meltable material, contained therewithin, absorbs energy and may change from a solid state to a melted state. Upon completion of the surgical procedure meltable material may cool to a temperature below the melting point of the meltable material and may re-solidify to a solid state.

During a surgical procedure a cooling apparatus may absorbed an amount of thermal energy such that material in the cooling apparatus melts and coaxial cable and/or cooling apparatus may approach an unacceptable temperature. Clinician may replace the heated cooling apparatus, containing the melted material, with an unheated cooling apparatus, thereby providing additional passive cooling for the coaxial cable. After the surgical procedure, or after heated cooling apparatus is removed from the coaxial cable, cooling apparatus cools and meltable material re-solidifies to a solid-like state.

Returning to FIGS. 4A and 4B, cooling apparatus 400 may contain a temperature sensor 470 to sense the temperature of the cooling apparatus 400. Temperature sensor 470 may include an indicator 470 a, such as, for example, a strip-type indicator or other suitable display, to provide the temperature of the cooling apparatus 400 to a clinician. Alternatively, sensor may include an electronic circuit (not explicitly shown) to measure and indicate a temperature. Electronic circuit (not explicitly shown) may include a means to communicate a temperature to a remote system, such as, for example, a computer or other suitable information collection system.

Active Cooling

Referring now to FIG. 5, a system for delivering microwave energy, including at least one cooling apparatus 500 according to an embodiment of the present disclosure, for actively cooling a coaxial cable 20 is shown as 10 a. The microwave delivery system 10 a includes a microwave generator 15, a coaxial cable 20 with at least one coaxial cable cooling apparatus 500 disposed on the coaxial cable 20, a system 40 for supplying cooling fluid and an electrosurgical energy delivery apparatus 30, including at least one microwave antenna 30 a capable of transmitting microwave energy.

Coaxial cable cooling apparatus 500 (hereinafter “cooling apparatus 500”) includes a cooling body or housing 505 configured to attached to at least a portion of the coaxial cable 20, at least one inlet member 545, and at least one outlet member 547. The one or more inlet members 545 and one or more outlet members 547 may be disposed in, formed by, or defined by housing 505.

Cooling fluid is supplied to the at least one inlet member 545 by cooling fluid supply 40 and circulated through at least a portion of the housing 505. The fluid circulated therethrough absorbs thermal energy generated by the coaxial cable 20 from the cooling apparatus 500, or any portion therewithin. Alternatively, the fluid circulating therethrough may absorb thermal energy directly from the coaxial cable 20. Fluid is discharged from the housing 505 through the at least one outlet member 547.

FIG. 6 illustrates a cooling apparatus 500, similar to cooling apparatus 200 of FIG. 2A, with a plurality of inlets 545 a-545 d disposed in the lower housing 505 b. Fluid is delivered to at least one of the inlets 545 a-545 d and circulated through the lower housing 505 b. A jumper hose 549 fluidly inter-connects to upper housing 505 a and lower housing 505 b to circulate fluid between the upper housing 505 a and the lower housing 505 b. Fluid is discharged from the cooling apparatus 500 through at least one of the plurality of the outlets 547 a-547 b disposed in the upper housing 505 a. Fluid circulated through housing 505 may absorb thermal energy from at least one of the lower housing 505 a, the upper housings 505 b and the material contained therewithin. Material may include a material with a high thermal mass and high energy absorbing properties as discussed herein.

Returning to FIG. 5, cooling fluid supply 40 may include a pump 41 for circulating the fluid, a cooling unit 42 for cooling the fluid returned from the cooling apparatus 500 through the return manifold 43. Fluid may be a thermally conductive fluid, such as, for example, water, saline, ammonium chloride, sodium nitrate, potassium chloride or any suitable fluid selected for the intended purpose of dissipating heat.

FIG. 7 illustrates yet another embodiment of a cooling apparatus 700 of the present disclosure. Cooling apparatus 700 includes a cooling body or housing 705, defining an inner lumen 730 and a channel 735, and an inlet 745 and an outlet 747 formed in the housing 705. Flap 740 connects to the housing 705 on one side of the channel 735 and attaches to flap attachment area 740 a on housing 705 on the opposite side of channel 735.

Cooling fluid is supplied to inlet 745 of housing 705, circulated through housing 705 before being discharged through outlet 747. Cooling fluid may be circulated through a portion of the housing 705 adjacent to and in thermal communication with the coaxial cable 20 to absorb thermal energy therefrom.

Turning now to FIGS. 8A-8C, yet another embodiment of a cooling apparatus 800, according to the present disclosure is shown. Cooling apparatus 800 includes a cooling body, or housing 805, having at least two tubes 850 a, 850 b, one or more attachment flaps 840, and defining one or more flap attachment areas 840 a. An inlet member 845 and an outlet member 847 may be fluidly connected to, or are integrally formed with, cooling tube 850 a and return tube 850 b, respectively. Fluid is supplied to inlet member 845 and is circulated though cooling tube 850 a and return tube 850 b. Thermal energy from the coaxial cable 20 and/or the cooling apparatus 800 is absorbed by the cooling fluid and is discharged through return tube 850 b.

With reference to FIG. 8A, cooling apparatus 800 is disposed on a coaxial cable 20. Cooling apparatus 800 is wrapped around the coaxial cable 20. Cooling apparatus 800 is secured on each end by flaps 840 that selectively attach to flap attachment areas 840 a.

The absorption rate of thermal energy from the coaxial cable 20 by cooling apparatus 800 is dependant on several factors. One factor is the contact surface area between the cooling and return tubes 850 a, 850 b and coaxial cable 20. The contact surface area between the cooling and return tubes 850 a, 850 b may be increased by forming cooling and return tubes 850 a, 850 b from flexible and/or malleable material such that when disposed on coaxial cable 20 the cooling and return tubes 850 a, 850 b conform to the surface of the coaxial cable 20. Cooling and return tubes 850 a, 850 b may be formed from any suitable tubing such as, for example, medical tubing and paratubes. Alternatively, cooling tube 850 a may be formed from a suitable material that conforms to the coaxial cable 20 and the return tube 850 b, which carries fluid already heated in the cooling tube 850 a, may be formed from a suitable material that does not conform to the coaxial cable.

In another embodiment of the present disclosure, the cooling tube 850 a contacts the coaxial cable 20 and the return tube 850 b is spaced away from the coaxial cable 20, thereby not making contact with the coaxial cable 20.

In yet another embodiment of the present disclosure, the at least one or more tubes 850 a, 850 b may be formed from multi-lumen tubing made from various materials such as, for example, polytetrafluoroethylene (PTFE), such as the material sold under the trademark Teflon™ and available from DuPont, perfluoroalkoxy (PFA), polytetrafluoroethylene (FEP) or expanded PTFE (ePTFE). The lumens of the multi-lumen tubing may be within one another, concentric, and/or separate and connected.

FIG. 8C is a transverse cross-sectional view of the cooling apparatus 800 of FIG. 8B formed from a multi-lumen tube 850. Multi-lumen tube 850 forms a cooling tube 850 a and a return tube 850 b with at least one common wall shared therebetween.

Referring now to FIG. 9, a system for delivering microwave energy, including at least one coaxial cable cooling sleeve apparatus 900, according to an embodiment of the present disclosure, for actively cooling a coaxial cable 20 is shown as 10 b. The microwave delivery system 12 includes a microwave generator 15, a coaxial cable 20 with at least one coaxial cable cooling sleeve apparatus 900 disposed on the coaxial cable 20, a system 40 for supplying cooling fluid and an electrosurgical energy delivery apparatus 30, including at least one microwave antenna 30 a, capable of transmitting microwave energy.

Coaxial cable cooling sleeve apparatus 900 (hereinafter “cooling sleeve apparatus”) includes a cooling body 905, configure to surround at least a portion of coaxial cable 20, at least one inlet 945, and at least one outlet 947.

Cooling fluid is supplied to the at least one inlet 945 by cooling fluid supply 40 via a conduit 40 a and circulated through at least a portion of the cooling body 905. Fluid circulated through cooling body 905, absorbs thermal energy generated by the coaxial cable 20 and/or from the cooling apparatus 900, and/or any portion therewithin. The heated fluid is discharged through the outlet 947 via conduit 40 b.

As seen in FIGS. 10A-10B and FIGS. 10C-10D, transverse cross-section views of two embodiments of the cooling sleeve apparatus 900 of FIG. 9 are illustrated. In FIGS. 10A and 10B, the housing 905 of a cooling sleeve apparatus 901 forms inner and outer concentric portions 951 a, 951 b, respectively, each forming at least one fluid tight chamber therewithin. In FIGS. 10C and 10D, the housing 905 of a cooling sleeve apparatus 902 forms a cooling portion 951 c and a return portion 951 d, each defining a fluid-tight chamber therewithin. In FIGS. 10A and 10C, the fluid-tight chambers are filled with fluid thereby pressing the inner surface 905 b of the housing 905 into the coaxial cable 20. Inner surface 905 b may be flexible and/or stretchable such that inner surface 905 b of the housing 905 and the outer surface 905 a of the coaxial cable 20 form suitable thermally conductive contact with one another.

With reference to FIG. 9 and FIGS. 10A-10D, the inlet 945 connects to the inner concentric portion 951 a of the cooling apparatus 901 in FIGS. 10A and 10B, or to the cooling portion 951 c of the cooling apparatus 902 in FIGS. 10C and 10D, and supplies cooling fluid thereto. The outlet 947 connects to the outer concentric portion 951 b of the cooling apparatus 901 in FIGS. 10A and 10B, or to the return portion 951 d of the cooling apparatus 902 in FIGS. 10C and 10D. Fluid enters housing 905 through the inlet member 945 and is circulated distally through the inner concentric portion 951 a or the cooling portion 951 c and absorbs thermal energy generated by the coaxial cable 20. In the distal portion of the cooling apparatus 900 fluid passes from the inner concentric portion 951 a to the outer concentric portion 951 b, or from the cooling portion 951 c to the return portion 951 d, through openings therebetween (not explicitly shown). Fluid then flows proximally through the outer concentric portion 951 b or the return portion 951 d and is discharged through the outlet 947.

In FIGS. 10B and 10D the fluid-tight chambers are not fluid-filled thereby defining a space or cavity 960 between the inner surface 905 b of the housing 905 and the coaxial cable 20. The shape of the cooling sleeve apparatus 901, 902 may be defined by a rigid or semi-rigid outer surface 905 a of housing 905. The shape may be maintained by the outer surface 905 a after a majority of the fluid is removed. Removal of fluid from the housing 905 may create a vacuum therewithin and may pull the inner surface 905 b of the housing 905 toward the outer surface 905 a thereby increasing the size or volume of space or cavity 960 between the inner surface 905 b of the housing 905 and the coaxial cable 20. Space 960 may be sufficiently large to allow the coaxial cable 20 to be threaded or inserted through space 960 thus providing a means of attaching the cooling apparatus 901, 902 to the coaxial cable 20.

The present application discloses apparatus and methods for cooling coaxial cables. It is envisioned that the various embodiments described hereinabove may be combined. For example, elements of the passive cooling apparatus may be applied to the various active cooling apparatus. While the embodiments contained herewithin are described in the context of cooling coaxial cables transmitting microwave energy any apparatus or method may be used to cool any cable, wire or elongated member. Modification of the above-described apparatuses and methods, and variations of aspects of the disclosure that are obvious to those of skill in the art are intended to be within the scope of the claims. 

1. A cable cooling apparatus for dissipating heat generated by a cable, the cooling apparatus comprising: a housing configured for attachment to at least a portion of a cable, the housing configured to retain a meltable material in a first state; and the meltable material configured to absorb thermal energy from the cable during transformation to a second state.
 2. The apparatus of claim 1, wherein the temperature at which the material transforms from a first state to a second state is between about 40° C. and about 100° C.
 3. The apparatus of claim 1, wherein the meltable material is selected from a group consisting of animal wax, insect wax, vegetable wax, mineral wax, petroleum wax, synthetic wax and an evaporative material.
 4. The apparatus of claim 3, wherein the animal wax is selected from a group consisting of Spermaceti and Lanolin.
 5. The apparatus of claim 3, wherein the insect wax is selected from a group consisting of Beeswax, Chinese wax and Shellac wax.
 6. The apparatus of claim 3, wherein the vegetable wax is selected from a group consisting of Bayberry wax and Candelilla wax, Carnauba wax, Castor wax, Esparto wax, Japan wax, Jojoba oil, Ouricury wax and Rice bran wax.
 7. The apparatus of claim 3, wherein the Mineral wax is selected from a group consisting of Ceresin wax, Montan wax, Ozocerite and Peat waxes.
 8. The apparatus of claim 3, wherein the Petroleum wax is selected from a group consisting of Paraffin wax and Microcrystalline wax.
 9. The apparatus of claim 3, wherein the synthetic wax is selected from a group consisting of a Polyethylene based wax, a chemically modified wax, substituted amide wax and polymerized α-olefins.
 10. The apparatus of claim 1, wherein the housing further includes: at least one inlet formed in the housing, the at least one inlet in fluid communication with the meltable material, and the at least one inlet configured to receive a fluid; at least one outlet formed in the housing, the at least one outlet in fluid communication with at least one of the inlets and the at least one outlet configured to discharge the fluid from the housing; and wherein the fluid is circulated through the housing from the inlet to the outlet such that the fluid absorbs thermal energy from the meltable material.
 11. The apparatus of claim 10, wherein the thermally conductive fluid is selected from the group consisting of water, saline, ammonium chloride, sodium nitrate, and potassium chloride.
 12. The apparatus of claim 10, wherein the cable is a microwave energy transmission cable.
 13. A cable cooling apparatus for dissipating heat generated by a cable, the cooling apparatus comprising: a housing defining a fluid-tight cavity therewithin, the housing disposed on at least a portion of a cable and configured to cool at least a portion of the cable, the housing including: at least one inlet configured to receive a fluid in the housing; and at least one outlet in fluid communication with the at least one inlet for discharging the fluid from the housing; wherein the fluid enters the housing through the inlet and wherein the fluid is circulated through at least a portion of the housing and absorbs thermal energy from at least a portion of the cable.
 14. The apparatus of claim 13, wherein the housing surrounds at least a portion of the cable.
 15. The apparatus of claim 13, wherein the housing further includes: a cooling portion in thermal communication with the cable; and a return portion for returning fluid through the at least one outlet.
 16. The apparatus of claim 13, wherein the cable is a microwave transmission cable.
 17. A method for cooling a cable during energy transmission through the cable, the method comprising the steps of: positioning at least one cable cooling apparatus adjacent an energy transmission cable; transmitting energy through the energy transmission cable; and dissipating heat produced by the energy transmission cable, during the energy transmission, through the at least one cable cooling apparatus.
 18. The method of claim 17 wherein the positioning step comprises uniformly positioning a plurality of cable cooling apparatus along the energy transmission cable.
 19. The method of claim 17 wherein the at least one cable cooling apparatus includes a selectively meltable material, the method further comprising causing the meltable material to change from a first state to a second state.
 20. The method of claim 17, further including the step of circulating a cooling fluid through the at least one cable cooling apparatus. 